Earlier known technology is described in FR-A1-2 660 755, which discloses a bubble detector that includes a conduit through which a first fluid having a first refractive index passes, a light source which directs a light beam through a first transparent wall part of the conduit, through the conduit cavity, and out through a second transparent wall part of said conduit, and a detector means which receives the light beam after it has passed through the conduit and the first fluid present therein. It is also disclosed in FR-A1-2 660 755 that the light beam shall be directed in a plane normal to the axis of the circular-cylindrical conduit and be directed non-diametrically through said conduit. With this construction, it is necessary to accurately adjust the position and direction of the light source with respect to refractive index (the first fluid/liquid concerned), and the position of the detector must be adjusted to receive the light beam. This known arrangement presumes that the refractive index of the fluid is constant and will record error functions already at relatively small variations in the refractive index of the fluid. The reliability of the known arrangement is also relatively poor, because the presence of bubbles in the fluid is detected by non-detection of a light beam by the detector. When the light beam passes a bubble, the beam is split and spreads so that no clear light beam will leave the conduit.
Among other drawbacks with the known arrangement is that it gives no clear indication of malfunctioning of the main components.
The object of the present invention is to reduce or eliminate at least one of these drawbacks.
This object is achieved with a bubble detector according to the accompanying Claim 1.